Nokea
Which of the following best describes the Gram stain process?
- A. It differentiates bacteria based on their flagella
- B. It identifies bacteria based on their shape
- C. It differentiates bacteria based on their cell wall structure
- D. It is used to determine bacterial motility
Correct Answer: C
Rationale: The Gram stain process involves staining bacterial cells with crystal violet and iodine, followed by decolorization and counterstaining. The primary differentiation is based on the cell wall structure, distinguishing bacteria into Gram-positive (retain purple color) and Gram-negative (lose purple color). This classification is crucial in microbiology for treatment decisions as it correlates with different antibiotic susceptibilities. Choices A, B, and D are incorrect because the Gram stain process does not primarily focus on flagella, shape, or motility of bacteria.
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A patient with fever and diarrhea had a stool sample that revealed Gram-negative rods that fermented lactose. What is the most likely causative agent?
- A. Escherichia coli
- B. Salmonella typhi
- C. Shigella dysenteriae
- D. Proteus vulgaris
Correct Answer: A
Rationale: The correct answer is A: Escherichia coli. E. coli is a Gram-negative rod that ferments lactose. It is a common cause of gastroenteritis presenting with fever and diarrhea. Salmonella typhi does not ferment lactose and causes typhoid fever. Shigella dysenteriae causes dysentery and does not ferment lactose. Proteus vulgaris does not typically cause gastroenteritis and is not known for lactose fermentation.
The bacteria that causes whooping cough is:
- A. Bordetella pertussis
- B. Haemophilus influenzae
- C. Pseudomonas aeruginosa
- D. Streptococcus pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Bordetella pertussis. Whooping cough is caused by this bacteria, which specifically infects the respiratory tract. Bordetella pertussis produces toxins that lead to the characteristic symptoms of the disease. Haemophilus influenzae, Pseudomonas aeruginosa, and Streptococcus pneumoniae are not the causative agents of whooping cough. Haemophilus influenzae can cause respiratory infections, Pseudomonas aeruginosa is associated with hospital-acquired infections, and Streptococcus pneumoniae is a common cause of pneumonia and other respiratory infections, but none of these bacteria are responsible for whooping cough.
In serologic reactions used in virology, a diagnostic antibody response should be taken into account if:
- A. A threshold increase in the titer in the second serum sample is observed
- B. The increase of the titer has no diagnostic significance for viral infections
- C. Two fold increase in the titer in the second serum sample is observed
- D. A fourfold increase in the titer in the second serum sample is observed
Correct Answer: D
Rationale: The correct answer is D because a fourfold increase in titer in the second serum sample indicates a significant rise in specific antibodies, which is crucial for diagnosing viral infections accurately. This increase is considered significant in serologic reactions as it shows a strong antibody response to the virus.
A: A threshold increase may not be substantial enough to confirm a diagnostic antibody response.
B: Dismissing the increase in titer would overlook important diagnostic information.
C: A twofold increase may not be as indicative of a strong antibody response compared to a fourfold increase.
A duodenal content smear of a patient with indigestion contains protozoa 10-18 mcm large. They have piriform bodies, 4 pairs of filaments, two symmetrically located nuclei in the broadened part of body. What kind of the lowest organisms is it?
- A. Lamblia
- B. Dysentery ameba
- C. Trichomonas
- D. Intestinal ameba
Correct Answer: A
Rationale: The correct answer is A: Lamblia. The description matches the characteristics of Giardia lamblia - a protozoan parasite that causes giardiasis. The piriform bodies, 4 pairs of filaments, and two symmetrically located nuclei are specific to Giardia lamblia. It is important to differentiate it from the other choices. Dysentery ameba (choice B) typically has a single nucleus and lacks the specific characteristics described. Trichomonas (choice C) is a flagellated protozoan with different morphology and does not match the given description. Intestinal ameba (choice D) such as Entamoeba histolytica usually has a single nucleus and different body shape compared to the described organism.
Which of these viruses is a laboratory product?
- A. Monkeypox
- B. Variola
- C. Vaccinia
- D. Cowpox
Correct Answer: C
Rationale: Rationale:
1. Vaccinia is a laboratory product used in smallpox vaccination.
2. Variola is the virus that causes smallpox, not a laboratory product.
3. Monkeypox is a naturally occurring virus, not a laboratory product.
4. Cowpox can be found in nature and is used in vaccine production, but it is not a laboratory product like Vaccinia.